Gingivitis is an early stage of the periodontal disease where the gums may become red, swollen and bleed easily. Gingivitis is usually painless and, if not treated, can advance to periodontitis, which may be classified by the magnitude of tissue destruction as mild, moderate, or severe. Periodontitis is primarily a disease of adults and is usually not detectable until after the age of 35. Usually bacteria that are present in dental plaque initiate periodontal disease. Toxins produced by the bacteria in the plaque activate the body's inflammatory and other immune mechanisms which ultimately lead to the destruction of the bone and gum tissue that support the teeth. As the disease progresses, the gums pull away from the teeth and periodontal pockets are formed which provide a protected environment for the bacteria, thereby causing the cycle to continue. However, some sites do not continue to be active. U.S. Pat. No. 5,328,829 discloses a method for determination of active periodontal disease sites within the oral cavity by measuring interleukin IL-1.beta. at the site. Smoking has been associated with an increased prevalence and severity of periodontitis. However, a significant number of individuals with periodontitis have never smoked.
For the past 15 years, there has been evidence that certain forms of periodontitis that affect young children and teenagers are genetically determined. These diseases, which are of extremely low prevalence in the population, produce severe periodontitis in some individuals before the age of puberty and in other individuals between puberty and age 18. The genetic factors that were identified in those cases involved very overt biologic mechanisms that most likely would predispose the individual to multiple health problems. To date, efforts to find the same types of genetic factors in adult forms of periodontitis have not been successful.
Genetic testing for disease prediction has been made possible (see U.S. Pat. Nos. 4,582,788 and 5,110,920) for diseases associated with or caused by one to two genes, once the genes are identified, to determine the risk of a person carrying a given gene for the disease (see for example U.S. Pat. Nos. 4,801,531, 4,666,828 and 5,268,267).
A genetic testing kit was developed to predicts risk for periodontal diseases using two variations in the human genome, one located in ILIA gene (ILIA+4845) and the other in IL1B gene (IL1B+3954). Carriers of at least one copy of the minor allele in each of these gene variations have increased susceptibility to periodontal disease. See U.S. Pat. No. 5,686,246. However, such a test has a limited utility in some ethnic populations and the test identifies only a small portion of people who are at risk for periodontal diseases in those populations. There is the need to find more sensitive method of determining risks of periodontal disease in all ethnic populations.